If you mean those ‘left
behind’ are referring to back-sliding Christians then I
would have to strongly disagree. What father would
leave behind his weaker child to suffer hell on
earth? Christ didn’t suffer on the Cross for the
sinless.

If you are referring to the
‘left behind’ as the lost then you bring an interesting
point. There are two camps: one that believes the
antichrist is revealed prior to the rapture; and the other
group is dogmatic that the antichrist will be revealed
AFTER the rapture.

So if then the AC is
revealed prior to the rapture, then the passage in Rev.
13:18 makes sense, as it is a warning to the wise,
discerning Christian, otherwise it would be possible that
the elect of God could be fooled by this evil man.
There are a lot of evil leaders out there, but just one
will be identified by the number 666.

On the other hand, if the
AC is ‘revealed’ AFTER the rapture, who is he being
‘revealed’ to? The damned? Those poor folks will be
given over to the grand delusion according to Scripture,
as they are damned by their own rejection of Christ.
What will be their purpose then of decoding the name of
the evil man, counting to 666, by the passage in
Revelation 13:18?

2Th 2:8-12 KJV -
[8] And then shall that
Wicked be revealed, whom the Lord shall consume with the
spirit of his mouth, and shall destroy with the
brightness of his coming: [9] [Even him], whose coming
is after the working of Satan with all power and signs
and lying wonders, [10] And with all deceivableness of
unrighteousness in them that perish; because they
received not the love of the truth, that they might be
saved. [11] And for this cause God shall send them
strong delusion, that they should believe a lie: [12]
That they all might be damned who believed not the
truth, but had pleasure in unrighteousness.